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Page name: The Engine [Logged in view] [RSS]
2005-02-23 18:07:03
Last author: Lord Asriel
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The Engine



   The Jack LaLanne of the engine world, GM's small-block V-8, ripples with newfound muscle thanks to a fatter bore and a longer stroke that yield 428 cubic inches or 7.0 litres of displacement. Coded LS7 (in 1970, GM advertised a 470-hp LS7 big-block V-8 that was never bolted into a production car), the latest ZO6's engine consists of a new aluminum-block casting liberally loaded with go-fast goodies. A forged-steel crankshaft is supported by six-bolt forged-steel main-bearing caps and is twisted by forged-aluminum connecting rods that are 25 percent lighter than the ferrous-metal rods used in the standard 6.0-litre V-8. Lighter cast-aluminum pistons sliding inside pressed-in cast-iron cylinder liners hammer the incoming charge with an 11.0:1 compression ratio. Intake and exhaust valves are lined up edge-to-edge, wall-to-wall. The 2.20-inch-diameter intakes are titanium for weight savings, and the 1.61-inch exhausts are sodium-filled for rapid heat transfer. An aggressive roller-follower camshaft kicks the valves open 13 percent wider than in the 6.0-litre V-8. All critical cylinder-head surfaces---intake and exhaust ports, combustion chambers---are fully machined to surpass the 6.0-litre engine's airflow by 18 percent. An electronically controlled 3.5 inch (90-millimeter) throttle meters air to the composite-plastic, tuned-length intake manifold, which is fed fuel by high-capacity solenoid injectors. On the exhaust side, four hydroformed stainless-steel tubes merge into one wide-mouth catalytic converter per bank. 

   The piece de resistance is a bona fide dry-sump lubrication system---a feature Porsche eliminated from its flat-sixes to save cost. A gerotor-type pump driven by the crankshaft evacuates oil that drains to the bottom of the block for storage in a cylindrical reservoir positioned in the right rear corner of the engine bay. A second pressure pump draws lubricant from the the tank for delivery to the engine's oil galleries. The key benefit with this arrangement is that there's no chance of oil starvation when high revs mix with high-g cornering and braking. Oil capacity is greater by 2.5 quarts (8.0 versus 5.5 in regular Corvettes), and the remote rservoir helps remove trapped air from the lubricant. To clear a spot for the tank, the battery has been relocated behind the right rear wheel.

   The LS7 generates a husky 500 hp at 6200 rpm, with a torque curve humped up to 475 lb-ft at 4800 rpm. That's 3.6 times the output of the original "Turbo-Fire V-8" engine that debuted in '55 Chevys, showing just how far a sound idea can go with half a century of development.



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